I. Field of the Invention
The present invention relates generally to wireless sensor networks, and particularly to wireless sensor networks configured to interact with the environment that they monitor.
II. Description of the Related Art
A wireless sensor network (WSN) comprises spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion, or pollutants, at different locations. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used for many civilian applications, including environment and habitat monitoring, healthcare applications, home automation, and traffic control.
Area monitoring is a typical application of WSNs. In area monitoring, the WSN is deployed over a region where some phenomenon is to be monitored. As an example, a large quantity of sensor nodes could be deployed over a battlefield to detect enemy intrusion. When the sensors detect the event being monitored (heat, pressure, sound, light, electromagnetic field, vibration, etc), the event is reported to a base station, which can take appropriate action (e.g., send a message on the internet or to a satellite). Depending on the application, different objective functions employ different data-propagation strategies, depending on one or more predetermined parameters, such as need for real-time response, data redundancy (which is typically handled via data aggregation techniques), need for security, etc.
WSNs are typically designed to be deployed in large numbers in various environments, including remote and hostile regions. Ad-hoc communications are employed for linking the sensors together. Algorithms and protocols have been developed to address issues associated with self-configuration, information routing, lifetime maximization, robustness, and fault tolerance.